F.A SANDOZ¹, V HERVE¹, V HERVE³, B DAUPHIN², J.R GRANT², S BINDSCHEDLER<sup>1

1</sup>Laboratory of Microbiology University of Neuchâtel, Neuchâtel, Switzerland, ²Laboratory of Evolutive Botany, University of Neuchâtel, Neuchâtel, Switzerland, ³Laboratory of Biogeosciences, Institute of Earth Sciences, University of Lausanne, Lausanne, Switzerland

Botrychium lunaria (Ophioglossaceae family), is a widespread fern that is completely dependent of a symbiosis with arbuscular mycorrhizal fungi (AMF) during all stages of its life cycle. Both the germination of spores and the formation of the achlorophyllous gametophytes occur entirely underground. Moreover, sporophytes produce their first emergent leaves only after 8 years. As a result, B. lunaria is under the total dependence of AMF communities in terms of carbon sources for a rather long period of time. In addition, the symbiosis remains important even after the emergence of mature sporophyte because of the particular root architecture that prevents for efficient foraging of nutrients in soils. This project aims at identifying the AMF communities associated to the roots of B. lunaria and the influences that biotic and abiotic factors have on the composition of these communities. We hypothesize that the alpha diversity of AMF communities of B. lunaria roots are related to the amount of carbon, nitrogen and phosphorous present in the rhizospheric soil of B. lunaria, but also to the alpha diversity of neighboring plants. In addition, we hypothesize that B. lunaria does not impose a selection for its AMF partners. Finally, we hypothesize that the four orders making up the Glomeromycota phylum are present in the roots of B. lunaria. In order to address these hypotheses, 72 soil samples without the presence of B. lunaria sporophytes and 72 B. lunaria sporophytes with their roots and their rhizospheric soil were sampled in four B. lunaria populations at the same altitude (2500 m a.s.l.). In total, 122 amplicons of the 18S rRNA gene (50 from soil samples and 72 roots samples from sporophyte root samples) were sequenced. In parallel, organic carbon, total nitrogen, total phosphorous, and pH were measured on rhizospheric soil samples. Preliminary results show that in total, 335 OTUs have been identified. Moreover, the sporophyte of B. lunaria is colonized by species of Glomerales, Diversisporales and Archaeosporales, with Glomerales OTUs being the most abundant ones. This study represents the first inventory of the AMF diversity of B. lunaria.